The present invention relates to a fuel injection pump for internal combustion engines having an adjusting piston which serves for adjusting an injection instant.
A fuel injection pump of this kind has already been disclosed by German Offenlegungsschrift 3,201,914. For the adjustment of the injection instant, this fuel injection pump has an adjusting piston which is arranged in a cylinder in a manner displaceable counter to a return force and, in the said cylinder, delimits a working space. A control slide is arranged in a blind bore in the adjusting piston in a manner displaceable counter to a return spring which is supported via an adjustable support in the cylinder. In the blind bore, the control slide delimits a pressure space which is continuously connected to a fuel-filled inlet chamber for supplying the pump working space of the fuel injection pump, the said inlet chamber being subject to pressure control as a function of speed. Acted upon by the pressure in the inlet chamber, the control slide performs a speed-dependent adjusting movement, the working space being connected to the pressure space or to a relief space or being held closed, depending on the position of the control slide relative to the adjusting piston. In the case of a deflection of the control slide out of a position in which it closes the working space, the adjusting piston executes a movement which follows the control slide after corresponding pressurisation or relief of the working space, the said movement being terminated by the reclosure of the working space. An adjusting movement of the adjusting piston in the direction of an earlier or later injection instant is executed accordingly. In order to allow for further operating parameters of the internal combustion engine operated using the fuel injection pump, the support of the return spring of the control slide can be adjusted by a servomotor. However, the servomotor takes up a large amount of installation space. Furthermore, pressure fluctuations in the inlet chamber of the fuel injection pump have an effect on the adjustment of the injection instant.